The St. Luke's\Roosevelt Hospital Center AIDS Clinical Trials Unit has been established to participate systematically in design, development and execution of clinical trials evaluating safety and efficacy of agents with therapeutic potential in AIDS, AIDS-related conditions and asymptomatic HIV infection. A number of serologic markers (including HIV P24 antigen, beta2-microglobulin, neopterin, soluble interleukin-2 receptor, soluble CD8 and soluble CD4) have been studied by us and other groups in persons with HIV infection and disease as possible prognostic indicators. Conversely, these markers which predict progression to AIDS possibly can be used as markers to monitor the effectiveness of treatment. We propose to study these markers as predictors of outcome in two recently completed multicenter placebo-controlled AZT trials of the ACTG (016 and the <500 T4 cell subgroup of 019) with the goal of establishing objective criteria for assessing intervention in HIV-seropositive persons. There is a clear need to determine the value of surrogate markers for prognosis of HIV infection, for selection of subgroups who would most benefit from early intervention and for use in assessing response to antiretroviral therapy. Sera from endpoint and matched non-endpoint participants are now available from protocols ACTG 016 and 019 and can be tested with these goals in mind. Given the increasing proportion of HIV-seropositive persons who are IV drug users and the need to determine prognostic and therapeutic parameters in this population, we propose to study IVDU subjects in 016 and 09 (<500 T4 cell subgroup) compared to homosexual patients.